Stay-at-home orders that brought armed protesters to the Michigan Capitol this spring may have saved tens of thousands of lives in the state, according to a British study.

Researchers at Imperial College London and Oxford University tracked the effectiveness of non-pharmaceutical interventions against the novel coronavirus, such as stay-at-home orders, by tracking how mobility decreased after governors declared states of emergency in each state.

They tracked mobility, using Google, because people who spend less time in public spaces are less likely to be exposed to the disease.  

The researchers found that states that were more successful at keeping people at home were also more successful at reducing the spread of COVID-19. And mobility decreased more in Michigan under Gov. Gretchen Whitmer’s stay-home orders than in any other Great Lakes states — or most states in the United States, according to the study

Investigators used the number of deaths from COVID-19 to calculate the rate at which the virus was being spread, starting after the first 10 deaths in each state. This “reproduction” rate represented the average number of people being infected by each person sick with COVID-19. 

In Michigan, as of about March 12 — before restaurants, businesses and schools were closed and prior to Whitmer’s stay-at-home orders — each person with COVID-19 was spreading the virus to about 3.5 other people, the study found. 

By mid-May, after mobility was reduced by Whitmer’s measures, the state’s reproduction number had fallen to 1, meaning sick individuals were spreading the disease to just one other person on average. 

Seth Flaxman, one of the study’s investigators and a senior lecturer in mathematics at Imperial College London, wouldn’t estimate how many lives have been saved so far by keeping Michigan residents out of public spaces. But a back-of-the-envelope calculation suggested an astounding number if nothing were done to curb the spread, he said.  

“The population of Michigan is 9 million,” Flaxman said. “In an unmitigated epidemic, you might expect that 70% to 80% of the population might be infected, that’s 7.4 million people infected with COVID-19.

“We assume around a 1% infection mortality rate — that’s over all the infections in the population, some are very mild. So if you multiple 7.4 million by 1%, you get 74,000 deaths,” he said.

Michigan has experienced 5,990 confirmed and probable deaths through Friday, according to the Michigan Department of Health and Human Services. Probable deaths are defined as people whose death certificates say they died of COVID-19 but they were never tested for the virus.

“There are lots of caveats, so it’s really hard to know,” Flaxman added, noting the actual number would depend on factors such as how quickly the virus spread, or hospitals became overloaded. 

According to the British team’s estimates, about 130,000 Michigan residents were infected with the disease at the end of March. By mid-May, the number of infected people had dropped to about 25,000 in the state. 

The yet-unpublished study was released online May 21. A similar study that focused on countries in Europe was published by the same team Monday in the journal Nature. Flaxman said the researchers will submit the report for publication after additional vetting. 

The state has had 65,672 cases confirmed and probable cases through Friday since the virus was first detected in early March. 

The British study was touted Thursday by the Whitmer administration, which has been criticized about the length of the strict stay-at-home orders, business closures and other restrictions during the outbreak. 

“Throughout this crisis, the vast majority of Michiganders have done the right thing by staying safer at home,” Whitmer said in a statement about the study. “Those who have done their part, especially the brave men and women on the front lines of this crisis, have helped us flatten the curve and save lives.

“Our action is working, but we must stay vigilant and flexible in order to lower the chance of a second wave.” 

The federal Centers for Disease Control and Prevention reported 1,994,283 confirmed cases of COVID-19 in the U.S. through Thursday, with 112,967 deaths. 

The British study estimated that about 4.1% of Americans had been infected through May 20 and predicted many more people will die as the economy opens up. 

“We predict that deaths over the next two-month period could exceed current cumulative deaths by greater than two-fold, if the relationship between mobility and transmission remains unchanged,” the authors wrote.

“Our results suggest that factors modulating transmission such as rapid testing, contact tracing and behavioral precautions are crucial to offset the rise of transmission associated with loosening of social distancing.”

The governor’s press release Thursday noted the state has significantly ramped up testing with more than 250 testing sites across the state.

Michigan has also expanded testing criteria to include anyone who exhibits symptoms, has been exposed to someone with symptoms, has been working outside their home for at least 10 days, or has been living or working in place, such as a homeless shelter or long-term care facility, where the disease could be easily spread. 

kbouffard@detroitnews.com

Twitter: @kbouffardDN

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